The famous reformer of the Roman Catholic Church during the Protestant Reformation was Martin Luther. His 95 Theses, posted in 1517, criticized church practices, particularly the sale of indulgences, and called for reforms within the Church. Luther's actions sparked significant theological debates and resulted in the formation of various Protestant denominations. His emphasis on personal faith and scripture as the authority reshaped the religious landscape of Europe. Luther’s ideas led to substantial social, political, and cultural transformations, marking a pivotal moment in Western history during the Reformation.